1314. Neonatal Serum Gentamicin Concentrations following Maternal Once-daily Gentamicin Dosing

Abstract

BackgroundGentamicin is commonly used for peripartum infections. Given literature supporting efficacy of once-daily dosing (ODD) of 5 mg/kg for chorioamnionitis, University of Chicago Medicine made the change from three times daily dosing (TIDD) to ODD. As gentamicin readily cross the placenta, it would be expected that maternal ODD would result in higher gentamicin neonatal serum concentrations following birth.MethodsThis was a single-center, retrospective chart review of all neonates born to mothers receiving peripartum ODD gentamicin within 12 hours of delivery between October 2019 and March 2020. A STAT random gentamicin serum concentration was obtained upon admission in neonates when initiation of antibiotics was desired. Specific dosing recommendations (Table 1) were developed utilizing neonatal population-based pharmacokinetics. The primary outcome was initial neonatal gentamicin serum concentration at birth. Other outcomes were also evaluated. Results were evaluated in two groups based on neonatal serum concentrations of less than 2 mcg/mL (Group 1) versus 2 mcg/mL or greater (Group 2).Table 1: Neonatal gentamicin dosing algorithm ResultsThirty-two mother-newborn dyads were included in this study. Baseline demographics are shown in Table 2. Newborns had a median gestational age of 39.4 weeks and median birth weight of 3.39 kilograms. The mean initial gentamicin concentration was supratherapeutic at 3.06 + 1.92 mcg/mL among all newborns (Table 3). The mean maternal dose in Group 1 (n=11) was 3.52 mg/kg (3.34, 4.77) based on actual body weight and 4.78 mg/kg (4.34, 5.18) in Group 2 (n=21) (p=0.025). The median time between maternal gentamicin administration and time of delivery varied between the groups at 0.5 hours versus 2.63 hours, respectively (p=0.005). All newborn gentamicin concentrations were less than 2 mcg/mL for maternal doses given less than 1 hour prior to delivery (n=8) (Figure 1). Overall protocol compliance rate was 81.3%. There were no significant differences in nephrotoxicity or ototoxicity between groups.Table 2. Baseline Demographics Table 3. Outcomes Figure 1. Comparison of maternal gentamicin time from administration to delivery and neonatal serum gentamicin concentrations ConclusionThis study suggests peripartum ODD of gentamicin may lead to clinically significant serum concentrations in neonates if administered between 1 to 12 hours of birth. Further studies are warranted to evaluate the effects of maternal ODD of gentamicin on newborns.Disclosures All Authors: No reported disclosures